there is a significant lag between hitting return and when I see the
debug output - 6-8 seconds.

I'm pretty sure this is a configuration problem or network problem on my
end as this same command in a different environment executes immediately.

To help me isolate where the problem is, is there another method to
debug what ldapsearch is doing before I see the first lines listed in
the debug output with -d 5? Or is there another utility I could use
than ldapsearch?

Try using strace and see what system calls get executed and where the
delay is. Alternatively you could try running ldapsearch under gdb and
interrupting it to get a stack trace from where the delay occurs.